/**
 * Created by Administrator on 2017/8/28 0028.
 */
function createTileLayer(){
    //当前地图名称
    var gridsetName = 'EPSG:4326';
    //分辨率级别名称
    var gridNames = ['EPSG:4326:1', 'EPSG:4326:2', 'EPSG:4326:3', 'EPSG:4326:4', 'EPSG:4326:5',
        'EPSG:4326:6', 'EPSG:4326:7', 'EPSG:4326:8', 'EPSG:4326:9', 'EPSG:4326:10',
        'EPSG:4326:11', 'EPSG:4326:12', 'EPSG:4326:13', 'EPSG:4326:14', 'EPSG:4326:15',
        'EPSG:4326:16', 'EPSG:4326:17', 'EPSG:4326:18'];
    var baseUrl = 'http://localhost:8080/geoserver/gwc/service/wmts';
    var style = '';
    var format = 'image/png';
    var infoFormat = 'text/html';
    var layerName = 'chinaMainLand';
    var projection = new ol.proj.Projection({
        code: 'EPSG:4326',
        units: 'degrees',
        axisOrientation: 'neu'
    });
    //分辨率单位，
    var resolutions = [0.3515625, 0.17578125, 0.087890625, 0.0439453125, 0.02197265625, 0.010986328125,
        0.0054931640625, 0.00274658203125, 0.001373291015625, 6.866455078125E-4, 3.4332275390625E-4,
        1.71661376953125E-4, 8.58306884765625E-5, 4.291534423828125E-5, 2.1457672119140625E-5,
        1.0728836059570312E-5, 5.364418029785156E-6, 2.682209014892578E-6];
    baseParams = ['VERSION','LAYER','STYLE','TILEMATRIX','TILEMATRIXSET','SERVICE','FORMAT'];

    params = {
        'VERSION': '1.0.0',
        'LAYER': layerName,
        'STYLE': style,
        'TILEMATRIX': gridNames,
        'TILEMATRIXSET': gridsetName,
        'SERVICE': 'WMTS',
        'FORMAT': format
    };
    //构建地图来源
    function constructSource() {
        var url = baseUrl+'?';
        for (var param in params) {
            if (baseParams.indexOf(param.toUpperCase()) < 0) {
                url = url + param + '=' + params[param] + '&';
            }
        }
        url = url.slice(0, -1);

        var source = new ol.source.WMTS({
            url: url,
            layer: params['LAYER'],
            matrixSet: params['TILEMATRIXSET'],
            format: params['FORMAT'],
            projection: projection,
            tileGrid: new ol.tilegrid.WMTS({
                tileSize: [256,256],
                //设定瓦片请求的范围，超过经纬度区间的瓦片不会发起请求
                extent: [73.0,13.0,140.9979061901028,54.13513078904522],
                origin: [-180.0, 90.0],
                resolutions: resolutions,
                matrixIds: params['TILEMATRIX']
            }),
            style: params['STYLE'],
            wrapX: true
        });
        return source;
    }
    //创建地图图层
    var layer = new ol.layer.Tile({
        source: constructSource()
    });
    return layer;
}